Antifouling coating films formed from curable organopolysiloxane antifouling coatings exhibit higher antifouling performance stably for a long term than conventional antifouling coating films produced from antifouling coatings based on hydrolyzable resins such as metal acrylate resins and silyl ester resins. The antifouling coating films formed from curable organopolysiloxane antifouling coatings have smaller elution of coating components into the sea, and are advantageous in terms of the prevention of environmental pollution.
Although antifouling coating films from curable organopolysiloxanes exhibit high antifouling performance in the sea against the attachment of macro organisms such as barnacles, bacterial secretions called slime become easily attached to the coating films. That is, these antifouling coating films have a drawback in that the resistance to fouling by slime (anti-sliming properties) is low.
Further, it is difficult for curable organopolysiloxane antifouling coatings to satisfy sprayability, coating film surface leveling properties and sagging resistance suited for spray operations with a good balance. Furthermore, difficulties are also encountered in designing curable organopolysiloxane antifouling coatings so that the coatings will maintain properties stably until they are used. In particular, the time available for the application to marine vessel shells is limited and therefore it is strongly demanded that thick films be formed in a small number of coating operations. However, a film thickness enough to ensure sufficient coating film strength and antifouling performance is difficult to realize with existing coatings in a small number of coating operations.
For example, Patent Literature 1 filed by the present applicant is directed to providing a cured organopolysiloxane antifouling composite coating film which is obtained by stacking, directly on the surface of an epoxy resin anticorrosive coating film, an organopolysiloxane antifouling coating film excellent in the interlayer adhesion with respect to the anticorrosive coating film as well as in antifouling performance. The cured organopolysiloxane antifouling composite coating film proposed for the direction includes:
[I] an epoxy resin anticorrosive coating film formed from an anticorrosive coating composition [i] comprising an epoxy resin (e1) and an amine-based, epoxy resin-curing agent (e2); and
[II] an antifouling coating film stacked directly on the surface of the epoxy resin anticorrosive coating film and formed from an antifouling coating composition [ii] comprising a curable organopolysiloxane composition, wherein
the curable organopolysiloxane composition is a three-component curable organopolysiloxane composition comprised of
(A) a main agent component containing an organopolysiloxane (a1) having at least two condensation reactive groups in the molecule, and silica (a2);
(B) a curing agent component containing an organosilane and/or a partial hydrolyzate thereof (b1) having functional groups capable of condensation reaction with the condensation reactive groups in the organopolysiloxane (a1); and
(C) a curing accelerator component containing a specific tin compound (ac).
Because of the direct coating on the epoxy resin anticorrosive coating film, the cured organopolysiloxane antifouling composite coating film of Patent Literature 1 can be completed in a short work period and exhibits excellent antifouling properties. However, the sagging resistance of the coating film is deteriorated during long storage and this makes it difficult to apply the coating in a large thickness. Further, although the formed coating film exhibits excellent antifouling properties and shows high effects in the prevention of macro fouling by organisms such as barnacles and Schizoporellidae, the attachment of slime takes place gradually.
Patent Literature 2 is directed to providing an anti-algae condensation curable organopolysiloxane composition displaying durable anti-algae performance and exhibiting excellent workability and water resistance, as well as to providing a coating method using the composition and a structure coated with the composition. The anti-algae condensation curable organopolysiloxane composition proposed for the direction is obtained by blending:
(A) a base polymer, in detail, an organopolysiloxane block copolymer which has at least two hydroxyl groups and/or hydrolyzable groups bonded to silicon atoms in the molecule, contains siloxane blocks represented by Formula (2): (R12SiO2/2)x (wherein R1 is an optionally substituted monovalent hydrocarbon group of 1 to 10 carbon atoms having no aliphatic unsaturated groups, and the letter x is an integer of 3 to 150), contains 30 to 80 mass % siloxane blocks represented by Average Unit Formula (3): R2SiO3/2 (wherein R2 is an optionally substituted aryl or alkaryl group of 6 to 12 carbon atoms) and having 3 to 150 silicon atoms, and has molecular ends at least partially terminated with units represented by Formula (4): R3R42SiO1/2 (wherein R3 is a hydroxyl group or a hydrolyzable group, and R4 indicates an optionally substituted monovalent hydrocarbon group of 1 to 10 carbon atoms having no aliphatic unsaturated groups);
(B) a silane and/or a partial hydrolyzate condensate thereof having two or more hydrolyzable groups in the molecule; and
(C) a specific urea compound (an anti-algae agent).
Although Patent Literature 2 describes that the coating film prevents the growth of algae, it is a drawback of the coating film that the resistance to the attachment of slime in seawater is not satisfactory. Marine vessels coated with such a coating film become fouled by slime, which deteriorates the functions of marine vessels and thus incurs frequent cleaning.
Patent Literature 3 is directed to providing an antifungal organopolysiloxane composition which can be cured to form silicone rubber with excellent weather resistance by occurrence of deoximation reaction. The organopolysiloxane composition proposed for the direction includes:
(A) 100 parts by weight of a silanol group-containing organopolysiloxane represented by General Formula (1): HO[Si(R1)2O]nH (wherein R1 indicates an optionally substituted monovalent hydrocarbon group, the plurality of R1s may be the same or different from one another, and the letter n is an integer of 10 or greater) and having a viscosity at 25° C. in the range of 25 to 500,000 cSt;
(B) 0.1 to 30 parts by weight of a hydrolyzable organosilane represented by General Formula (2): (R2)aSi[ON═C(R1)2]4-a (2) (wherein R1 is the same as defined above, R2 indicates a monovalent aliphatic hydrocarbon group, and the letter a is 0 or 1) and/or a partial hydrolyzate thereof;
(C) 0.1 to 5 parts by weight of a triazolyl group-containing antifungal compound; and
(D) 3 to 100 parts by weight of an organopolysiloxane represented by General Formula (3): (R7)3SiO[Si(R1)2O]mSi(R7)3 (3) (wherein R1 is the same as defined above, R7 is similar to R1, and the letter m is an integer of 0 or greater) and having a viscosity at 25° C. that is 1/200 to 2 times greater than that of the component (A).
Although Patent Literature 3 describes that the coating film prevents the growth of algae, it is a drawback of the coating film that the resistance to the attachment of slime in seawater is not satisfactory. Marine vessels coated with such a coating film will lower functions as marine vessels due to the development of fouling by slime, thus requiring frequent cleaning.
Patent Literature 4 filed by the present applicant is directed to providing a curable composition which is excellent in properties such as low viscosity and high thixotropy with a good balance, can be applied in a large thickness in one coating operation, and can give a cured coating film exhibiting excellent properties such as rubber strength and surface smoothness with a good balance. The curable composition proposed for the direction, which can be used as an antifouling coating composition, contains: (A) an organopolysiloxane having condensation reactive functional groups at both ends of the molecule; and (B) hydrophobic silica, wherein the hydrophobic silica (B) has been heat treated together with the organopolysiloxane (A).
Although the curable composition (antifouling coating composition) of Patent Literature 4 can give coating films with a uniform film thickness and excellent long-term antifouling performance, it is difficult for the composition to form coating films having a film thickness required to protect marine vessel shells in one coating operation without the occurrence of sagging. Further, the coating films have a drawback in that the coating films are easily scratched by contact with objects floating on the sea.
Patent Literature 5 filed by the present applicant is directed to providing a curable composition which is excellent in properties such as low viscosity and high thixotropy with a good balance, can be applied in a large thickness in one coating operation, and can give a cured coating film exhibiting excellent properties such as rubber strength and surface smoothness with a good balance. The curable composition proposed for the direction, which can be used as an antifouling coating composition, is produced by heat treating part or the whole of an organopolysiloxane (A) terminated with hydroxyl groups or hydrolyzable groups at both ends of the molecule, together with at least one of hydrophobic silica and hydrophilic silica (B) at a temperature of from 100° C. to the decomposition temperature of the components, and thereafter, if there is any remaining portion, adding at least the remaining portion of the component (A) and the component (B) to the resultant heat treated product.
However, similarly to the composition of Patent Literature 4, it is difficult for the curable composition (antifouling coating composition) of Patent Literature 5 to form coating films having a film thickness required to protect marine vessel shells in one coating operation without the occurrence of sagging. Further, the coating films have a drawback in that the coating films are easily scratched by contact with objects floating on the sea.
Patent Literature 6 discloses a fouling control coating composition comprising a polysiloxane-based binder system, 0.01 to 20% by dry weight of one or more hydrophilic-modified polysiloxanes, and one or more biocides. For example, the hydrophilic-modified polysiloxane is a polysiloxane having incorporated in and/or grafted to the backbone thereof a poly(oxyalkylene)-modified polysiloxane.
The coating composition of Patent Literature 6 is characterized in that the composition exhibits antifouling performance by the hydrophilic-modified polysiloxane facilitating the leaching of the biocides. However, the hydrophilic-modified polysiloxane has low compatibility with the polysiloxane that is the base resin in the coating composition. Because of this low compatibility, coating films formed from the coating composition tend to have problems in that the adhesion with respect to surfaces and the uniformity in coating film appearance are variable depending on the conditions in which the coating composition is applied.